Endless Hose of Tropical Moisture for the East Coast

The Southeast, especially Florida, is in for a very wet and ugly week, but this ugly weather isn’t all bad news. Not only will the cloud cover and rain allow for cooler temperatures with highs in the 80s, but some locations are experiencing a drought. Much of this rainfall, which will amount to inches, will improve or even wipe out the current drought conditions. The worst of the drought is located in South Florida. Cities like Miami and Naples are in a severe drought. Southeastern Georgia is also experiencing a severe drought while a moderate drought impacts various locations of the Southeast.

On Monday, cities like Miami and Tampa may experience record atmospheric moisture as precipitable water values exceed two inches across much of the Florida Panhandle. Below is the atmospheric climatology for Tampa. We highlighted the data for May 14th, which shows a record precipitable water value of 2.05 inches, but this year values may near 3 inches. That indicates an extremely moist and record-moist atmosphere.

Precipitable Water Climatology for Tampa, FL

In terms of your forecast on Tuesday, we don’t think there will be a widespread area of rain but there will be widespread rounds of rain and thunderstorms that move through the Southeast. This includes all of Florida, most of Georgia and South Carolina, and portions of Alabama and North Carolina. This tropical air will also seep into the Plains and Ohio Valley, where severe storms will be possible. These storms will be heavy due to the influx of tropical moisture.

On Wednesday, a new enhancement of precipitable water will begin to work into Florida from the Gulf of Mexico, so another rounds of widespread rain and thunderstorms will be likely statewide, and many locations will experience heavy rain. Further north, scattered showers and storms will be found across the Southeast, Appalachians Mountains, and into the Mid-Atlantic region. Some of these showers will contain heavier downpours thanks to the saturated air mass.

The most rich atmospheric moisture will become the most widespread on Thursday. Much of the Southeast and Mid-Atlantic coastal areas may record over 2 inches of water in the sky during this time period. This is a big signal for the risk of heavy rain and even flash flooding. Thankfully, the risk for flooding is on the lower end due to near to below average rainfall totals so far this year. There will also be the potential subtropical cyclone that moves onshore and into the Southeast from the Gulf of Mexico by Thursday, so that will chance rainfall totals across the Florida Panhandle and parts of Alabama and Georgia. Otherwise, widespread showers and storms will persist across the Southeast, Appalachians, Tennessee Valley, and Mid-Atlantic. Once you go west of the Mississippi River and north of the Ohio River, it will be mainly dry.

Predictable Water Forecast Friday

Then on Friday into Friday night, the deep tropical moisture will surge into the Northeast and New England, especially by the coast as a strong Bermuda High directs it. While the surface low from the Gulf of Mexico makes its way into the eastern Gulf of Mexico and interior Northeast, bring rain and pockets of heavier rain, a widespread rain will also be found in the Mid-Atlantic and southern New England. Scattered showers and thunderstorms will also persist in the Southeast and Florida, although the Mississippi River and western Ohio River Valleys should dry out.

While the deepest of moisture moves offshore from the Northeast, precipitable water values of over 2 inches will remain in place across Florida on Saturday. The Sunshine State won’t be so sunny during the weekend as well. Widespread rain and storms will still be around while the activity is more scattered up the East Coast in the Southeast, Mid-Atlantic, and Northeast.

By Sunday, a cold front will allow for a brief break from the rain in the Northeast and northern Mid-Atlantic region, showers and storms will remain in the picture from the southern Mid-Atlantic region through Florida. The greatest risk for heavy rain will be found in Florida.

After Monday of next week, the weather pattern across the Eastern US should settle down, at least become quieter than this week’s weather, as the tropical tap of moisture shuts off. May 15th marks the start of Florida’s wet season, so typical showers and storms can be expected in the state and the Southeast as well.

Rainfall will be quite heavy thanks to this deep tropical moisture from the Caribbean Sea. Some locations may receive up to ten inches of rain in Florida while a widespread 2 to 3 inches falls across the Eastern US through Monday night.

Jackson is Head of Content at WeatherOptics and produces several forecasts and manages all social media platforms. Previously, Jackson forecasted local weather for southwestern Connecticut, founding his website, Jackson's Weather, in the March of 2015. He is currently studying Meteorology and Broadcast Journalism at the University of Miami.